1. Field of the Invention
The present invention relates to an optical information recording medium, and in particular, to a multilayered optical disk.
2. Description of the Related Art
An optical disk, which is one kind of optical information recording media, is widely used to record and reproduce various data including audio and video data. Such optical disks include a compact disk (CD), a digital video disk (DVD), a laser disk (LD), and a mini disk (MD). Among them, the CD is a major optical disk which has widely been used so far, and the DVD has recently emerged. The DVD is expected to find wide use as a next generation recording medium for recording and reproducing video and audio data because it can accommodate 17-GB data at a maximum, enough to store one movie on a single disk, using high-density digital compression technology, though it is only as large as a conventional CD, provides higher image quality than the LD, and allows simultaneous dubbing of a plurality of languages for a movie to be appreciated in a selected language.
Meanwhile, CDs and their reproducing devices are widely used in audio systems, whereas DVDs and their reproducing devices have just started to be provided. Hence, the CDs will be more popular than the DVDs at least for the time being. In this context, it is preferable to fabricate a DVD which can be compatibly reproduced in both CD and DVD reproducing devices.
However, CD and DVD systems differ in standard (format), wavelength of light used for reproducing data, and mechanical mechanisms. That is, light sources as provided in CD and DVD standards are a 780 nm infrared laser and a 680-635 nm red laser, respectively. Besides, a CD is 1.2 mm thick, while a dual DVD currently used is a stack of two 0.6 mm-thick disks with their respective recording layers attached to each other to allow recording and reproduction of data on and from both surfaces.
As described above, a single optical disk cannot accommodate both types of data separately reproducible in a conventional CD reproducing device and a DVD reproducing device.
Therefore, due to its inability of satisfying different standards of reproducing devices, the optical disk cannot be used concurrently and compatibly for different purposes. The same problem is encountered when different light sources or mechanical mechanisms are used for different standards.
Accordingly, an object of the present invention is to provide an optical disk satisfying different standards.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects of the present invention, there is provided an optical disk. The optical disk includes a first recording layer for recording data reproducible only by an optical disk reproducing device using light of a wavelength based on a first standard, and a second recording layer for recording data reproducible only by an optical disk reproducing device using light of a wavelength based on a second standard different from the first standard.
The feature of the present invention lies in the fact that an optical disk has a first recording layer and a second recording layer for recording data reproducible only in a first standard wavelength using a first type of optical disk reproducing system and in a second standard wavelength using a second type of optical disk reproducing system, respectively.
For this purpose, first and second disks are prepared, with a total thickness of both disks attached to each other set according to a first standard, and a thickness of the second disk set according to a second standard.
The first disk includes a recording layer formed according to the first standard, and a selective reflection layer with a high reflectance for light of a first standard wavelength and a high absorptance for light of a second standard wavelength. On the other hand, the second disk includes a recording layer formed according to the second standard, and a semi-transmission film with a high transmittance for the light of the first standard wavelength and a reflectance as provided by the second standard for the light of the second standard wavelength. A surface of the first disk, opposite to that of the selective reflection layer, is attached to the semi-transmission surface of the second disk having the semi-transmission film by a transparent adhesive, so that a total thickness of both disks is set according to the first standard.
In this disk structure, a first standard optical disk reproducing device can reproduce data recorded according to the first standard by reflecting a first standard laser beam from the selective reflection layer of the first disk. On the contrary, a second standard optical disk reproducing device can reproduce data recorded according to the second standard by reflecting a second standard laser beam from the semi-transmission film of the second disk.
Thus, data supporting a plurality of standards are recorded in different recording layers, and produced by corresponding standard optical disk reproducing devices.